190 Trans. Acad. Sci. of St. Louis. 
modified form of the apparatus used by Boys will be re- 
quired. The necessity for such a construction seems to 
be justified by the evidence already obtained, that if the 
potential of either of the attracting masses M and m’ is 
zero absolute, gravitational attraction between them will 
not be affected by varying the potential of the other 
mass. The gravitation, constant as it has been deter- 
mined by methods which made use of some form of the 
Mitchell-Cavendish apparatus, would have a maximum 
value when either or both of the masses had a potential 
of zero absolute. 
Neglecting the inductive effect which electrified masses 
have upon each other, it is possible that the amended 
equation for gravitational attraction between them is 
_— mm’ , DY 
A=K—> — Kk = * 
It seems possible that the effect of the charges @ and 
Q’ upon gravitational attraction between the masses ™ 
and m’ may be a surface effect. If so the values of Q 
and @’ may be replaced by RV and R’ V’, where R and 
R’ are the radii of the two masses and V and V’ their 
potentials due to those charges. 
The above equation may also be written 
n \mm’ 
4=K(i— nn) “~ 
Here it is assumed that the masses are so electrified as 
to diminish their normal attraction for each other by ” 
per cent. From these two equations the values of m and 
m” being replaced by their values in terms of volume and 
density. 
She AG pe i de 
a oe 
If this equation really represents the conditions im- 
posed upon the masses, it appears that for any given de- 
crease in gravitational attraction the potentials of the 
masses must be directly proportional to the surface areas 
